<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>CORS</title>
</head>
<body>
    <div class="container"></div>

    <script>

        const url = 'http://localhost:3000';
        const data = {username:'daxia'};

        const myHeaders = new Headers({
            'X-Custom-Header':'xxx'
        });

        fetch(url,{
            method:'POST',
            body:JSON.stringify(data),
            headers:myHeaders,
            mode:'cors',
            Origin:'http://localhost:5500'
        })
            .then(res => res.json())
            .then(data => console.log(JSON.parse(data.postData)));


    </script>
</body>
</html>